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Measurements >> Other Measurements >> how to measure phase margin in real chip?
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Message started by vlado on Jun 4th, 2004, 1:10am

Title: how to measure phase margin in real chip?
Post by vlado on Jun 4th, 2004, 1:10am

Hi, I need to measure phase margin in real chip. It is low drop out regulator and i need to know how stable is that circuit. Open loop measurement isn`t so exact, i thing...
thanx

Title: Re: how to measure phase margin in real chip?
Post by Frank Wiedmann on Jun 4th, 2004, 4:20am

Do you mean measurement in the lab or simulation? If you mean simulation: Spectre 5.0 has a stability analysis (stb) that keeps the loop closed. If you mean measurement in the lab: take a look at http://www.venable.biz/tr-papers2.html.

Title: Re: how to measure phase margin in real chip?
Post by vlado on Jun 7th, 2004, 2:11am

i mean real measurement in lab, SPICE simulation is quit simple, but in real it is problem.

Title: Re: how to measure phase margin in real chip?
Post by sheldon on Dec 28th, 2004, 6:08pm

Vlado,

  Never measured phase margin on the bench so it is a good question. Have you tried putting in a small square wave, need to avoid slew rate limiting, and looking at the overshoot? You should be able to infer phase margin from small signal overshoot. Don't remeber the formula for conversion, it is in most textbooks, Gray and Meyer and Allen.

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